"Mechanically Docked" Metallodendrimers about Single-Walled Carbon Nanotubes

We report experimental support for "mechanical docking" of an optically active rigid molecule, ruthenium metallodendrimer (decamer), to single-walled carbon nanotubes (SWNTs) with some diameter selectivity. Binding of these rigid metallodendrimers onto dispersed single-walled carbon nanotubes has been studied by Raman and UV-vis-near-infrared (NIR) absorption spectroscopy. Atomic force and scanning electron micrographs indicate strong binding of these molecules specifically to the ends of nanotubes and are consistent with the spectroscopic evidence for diameter selectivity presented here. Near-IR absorption and radial breathing mode Raman spectra of these "end-functionalized" SWNTs show preferential diameter-selective separation, along with a red shift of the optical transitions. A con central ion-dependent red shift is observed for the NIR absorption for decamer-bound nanotubes. This indicates a strong interaction between selective SWNTs and the decamer, forming a mechanically docked supramolecular complex. Spectral shifts and intensity variations in specific radial breathing mode bands of the functionalized SWNTs are complementary to our observations of the UV-vis-NIR absorption spectra and atomic force microscopy data.